The present invention relates to an image-reading apparatus.
In recent years, there has been well-known an image-reading apparatus, which reads an image recorded on a photographic film or a photographic print (hereinafter, referred to as a photographic image, for the general term of them) by means of an image sensor to acquire image data. For instance, a film scanner, being an example of such the image-reading apparatus, acquires the image data by conducting the steps of: irradiating light, emitted from a light emitting means such as a halogen lamp, etc., onto the developed photographic film on which the image is already formed, while conveying the photographic film; photo-electronically reading the light penetrated through the photographic film by means of a photo detecting element, such as a CCD (Charge Coupled Device), a line sensor, etc.; and applying an analogue-to-digital conversion processing (hereinafter, referred to as A/D conversion processing, for simplicity) to the read image signals so as to acquire the digital image data (set forth in Tokkai 2003-110823, Japanese Non-Examined Patent Publication). Further, when the scanner acquires the image data from the photographic print, the photo detecting element receives the light reflected from the photographic print, and then, the same steps as the above will be conducted (set forth in Tokkai 2002-277977, Japanese Non-Examined Patent Publication).
In the conventional image-reading apparatus mentioned in the above, the halogen lamp has been generally employed as the light emitting means for irradiating the light onto the photographic image. It is impossible, however, to control a light emitting amount for every color, when the halogen lamp is employed for the light emitting source. Accordingly, there has been a problem that the color balance of the image reproduced from the read image data would be deteriorated due to the following reasons.
FIG. 1 shows an example of a base penetrated light amount of a negative film for every color.
As shown in FIG. 1, since the base penetrated light amount (defined as an amount of light only penetrated through a substrate, a subbing layer, a filter layer, etc., irrespective of contents of the image, namely, a penetrated light amount at a non-image area) varies with the wavelength range of the light emitted from the light emitting source, namely, colors (here, R (Red), G (Green), B (Blue)), the base penetrated light amounts of colors R, G, B could not coincide with each other, resulting in a deterioration of the color balance. With respect to the reflectivity of the photographic paper for printing use for every color, that goes as well.
According to the description set forth in Tokkai 2003-110823, to cope with the abovementioned problem, the RGB balancing filter is mounted between the light source and the photographic image to be read. As a result, however, the apparatus becomes complicated and large-sized.
As another solution for the abovementioned problem, proposed is a technology for improving the image quality of the read image by employing the LED (light Emitting Diode) as the light emitting source of the image-reading apparatus so as to control the light emitting amount and/or a light amount distribution for every color of the LED (for instance, set forth in Tokkai 2003-233142, Japanese Non-Examined Patent Publication). With respect to the light emitting action of the LED, employed is a method of simultaneously emitting all color lights and stopping the emission of each color light corresponding to the predetermined light amount (namely, the stopping time points of the color lights are different from each other).
Referring to FIG. 8(c), an example of the abovementioned method will be detailed in the following.
FIGS. 8(a)–8(d) show a gradation distribution in a gradation scale as a typical model, indicating a comparison between the gradation distribution and the LED light emitting timing of each color within one scanning period.
FIG. 8(a) shows the gradation scale, while FIG. 8(b) shows a graph of the gradation from highlight to shadow corresponding to the gradation scale as a typical model.
Further, FIG. 8(c) shows a duration time of the light emitting action currently in use of the LED serving as a light emitting source of each color (B, G, R, IR (infrared)), a start-time point of starting the light emitting action and a stop-time point of stopping the light emitting action. The output level of each color light is established at constant level E. Accordingly, the light emitting action of the LED for each color light starts at the same time, and then, stops corresponding to the predetermined light amount of each color.
However, since the gradation distribution exists even within a unit of gradation scale as shown in FIG. 8(a) and FIG. 8(b), the gradation distribution, which can be covered by the timing and the duration of the light emitted by the light emitting element, differs for every color as shown in FIG. 8 (c). On the other hand, since the light receiving element detects the center of integrating the gradation distribution, which corresponds to the distribution of the light receiving amount, as the gradation, the center of integrating the gradation distribution for every color deviates (namely, the detected value of the gradation deviates) even if the gradation scale is the same. This causes a deficiency of deteriorating the color-balance of the reproduced image outputted on the basis of the acquired data.